Apparatus for electrical sound reproduction



May 29, 1928. 1,671,292

J. J. JAKOSKY APPARATUS FOR ELECTRICAL SOUND REPRODUCTION Filed July 23, 1926 INVENTOR. 1/0/9/7 d. JVA/05k] ATTORNEYS.

" pal objections has ramas ay 29, 192s.

En STATES vPAT-Erri"Y .,oFFi'CE.

earns, cALironNIA, Assieivon To INTERNATIONAL PRE- Los Ane-Enns, CALIFORNIA, A conformaron or CALI- FORNIA.

APPARATUS FOREELECTRICAL SOUND REPRODUCTION.

Appiicatioa mediuiy 23,

i This invention relates to apparatus for the electrical reproduction and amplification of sound from a phonograph record, and the main object of the invention is to improve the quality of such reproduction and particularly to eliminate substantially entirely the scratching` noise resulting fromv the passage of the needle or stylus over the record.

In the mechanical reproduction of sound from phonograph records one of the princibeeii the constant scratching noise which was produced due to vibrations of extremely high frequency imparted to4 the phono herent roughness or face of the record.

graph stylus by the inirizegularity of the sur- It has`recently` been found that by means of electrical reproduction this scratching.

noise may be largely reduced. and the quality of reproduction greatly improved.

I have found, however,

that in the means heretofore proposed for the electrical reproduction`and 'amplifica tion of sound'from a phonograph record, the

scratching noise is not entirely eliminated and l have found furtlrer that the scratching iioise which is otherwise present in electrical reproduction eliminated by placing of suitable capacity may be' substantially a by-pass condenser at a suitable point in the circuit, for exuample directly across the terminals of the secondary winding of one system alternatively in used' for amplification, .last transformer in the I have further found that when it utilize the same amplifying conjunction either with a radio receiving set or with an electrical phonograph sion of such a bythe inclureproducer,

of said pass condenser suitable value at the point mentioned is undesirable for use in conjunction with the radio receiving set,

and it is therefore desirable to provide means Awhereby said cone denser is connected in the same is used in electrical reproduction clusion of a by-pass point in the circuit as the circuit only when phonograph condenser at a suitable above. mentioned, but

also includes a suitable switching device whereby suoli by-p ass condenser may be automatically connected in the circuit when the amplifier is to be used in conjunction.

only the in-Y -isza serial ire-124,396. v

with electrical phonograph reproduction and maybe automatically disconnected from thel plication of my invention to an amplifying system adapted for use i-n connection with either a radio receiving set or an electrical phonograph reproducer.

Fig..2 is a vertical section of the switching means illustrated diagrammatically in ,Fig 1. l

Fig. 3 'is a Wiring diagram showing another modificationl of the invention in which the switching device -is also adapted to disconnect the detector tube of the radio receiving set and insert a compensating resistance when the phonograph reproducer is connected to the amplifying means. .The'amplifyingl system shown in Fig. l comprises two amplifying transformers 1 and 2 and two tlierinionic tubes 3 and 4 each provided with grid 5, filament 6, and plate 7. Said parts are provided with the usual A, B, and C battery connections as shown.

In the drawings I have shown the 4ain- Vplifying system above described as forming part of a 'radio receiving set but itwill be understood that the 'phase of my invention which relates solely to the inclusion of a by'- pass condenser in shunt across the secondary winding of an amplifier vtransformer, and

preferably of the last transformer, is'applicable in connection with any electrical amplifying-means whether the same `be conn nected to a radio receiving set or whether it be a separate unit or whether it be intended solelyfor use in connection with electrical phonograph reproduction.

rlhe radio receivin l also comprises at ermionic detector tube set illustrated in pliiicr. For ef 12 having grid 13, filament 14, and plate 15. The system further comprisesy antenna 16,

ground connection 17, primary and secondary coils 18 and 19, condenser 20,`vari-'.

tion withA any suitable. means ol electricalV phonograph reproduction, such means comprising essentially a device which is adapt-` ed to produce electrical impulses corresponding in frequency and intensity to the undulations of the phonograph record and said device being connected to the input of an electrical amplifying system. ln Fig. l I have-illustrated diagrammatically one type of means 'for Vproducing electrical impulses as above described, such means comprising a needle-carrying member 25 adapted to hold a phonograph needle indicated at 26 and secured to a lever member or rocking member 27 mounted to rock between rubber pads indicatedv at 28 and 29. Lever member 27 is connected lat one side of thc axis about which it rocks-to a translatingl member such as wire 30 whose other end is connected to one end of armature 3l which is mounted in any suitable manner to rock about aniaxis extending through its midpoint 32 and perpendicular to the plane. ot the drawing. A ,permanent magnet 232i is provided with pole pieces 34 and at the respective sides of armature 3l so that when said armature rocks between said pole pieces the magnetic flux therethrough varies in di- -rection and intensity. An electrical coil 36 is provided around armature 31, said coil being either adapted to rock with the armature or being mounted in stationary position surrounding the same. scribed. device forms no essential part ot this invention but is .more fully described and claimed in my copending application Ser. No. 102,100', liled April 15, 1926.

The output terminals of the above described device, or oil any other suitable dcvice for producing electrical impulses correspondingto the umlulations ot a phonograph record, may be connected in any suitable manner to the input ot an electrical amplifying system lor example to the terminals of the. primary lwindingl of trans,- t'ormer 1. For the purpose et my invention, andl in any when itis desired to permit utilization ot a single amplil'ying system alternatively in cmijunction with radio reception or electrical reproduction, l

i prefer to provide detachable connecting means between the reproduccr and the amnple the ends Toi? coil4 5:36 be connected by' wire 40 and 4l to the contact portions 42 and 4.5 respect' Contact plug' 44 which is adapted :tor

The above detion in acontact jack indicated diagrammatically at 45 in'F ig. 1 and shown more 1n detail in Fig. 2. A suitable rheostat 46 may l beinserted in one of the wires 40 or 4l for varying the intensity of current therein Aand hence varying the `volume of'sound production;

lReferring now to Fig. 2 in conjunction with Fig, l, the jack 45 may comprise a contact .member 48 having a sleeve portion 49 through which plug 44 is adapted for insertion in such manner as to make connection lcontacts 57 and 58, the lower one ot which is adapted to be raised, as by means olinsulating pin 59, when the contact spring 50 is raised by insertion of the connecting plug as above described, so as to make connection at 6() between contact members 5T and., 5S. Contact member 57 is connected to binding post 62 and contact member 5S is connected to a condenser 63 ot any suitable type and ot' sul'licient capacity'to substantially by-pars all current impulsesot` higher trequeimvthan the sounds which are intended io be reproduced. Condenser (S3 is in turn conncctcd to bindingpost 64. Binding msts 62 and 64 may be connected respectively by wires (i5 and 66 to the two terminals ol1 the secondary winding ot transformer Q.

The jack 45 may if desired be niounted in a suitable casing 67 having one end formed as an insulating base GS on which are mounted thebinding posts 5l, 52, 62, and 64. Sleeve portion 49 may be externally threaded and may be provided with a nut. 69 so as to permit mounting` ot the jack on the panel oit a radio receiving set or an amplifier, in the usual manner of such devices. member 48 may be iormcdas a supporting base lor the jael; in the usual mam'icr ot such. devices, the other contact members lbeing mounted thereon by means of screws Contact riable condenser amplifying system as it may be applied inl connection, with any ordinary thermionic.

tube amplier.

rlhe operation ofl the apparatus and cir: cuits above described is as follows:

When itis desired to use the circuit for radio receptionthe plug 44 is removed from jack 45 thus breaking connection between the electrical phonograph reproducer and the amplifying system, and also ing condenser 63 from the circuit. The circuit then operates in the normal manner of radio receiving circuits. lVhen, however, it is desired to utilize .the circuit for electrical phonograph reproduction the radio receiving circuit is detuned'as by means of va- 'll's'o as .to prevent radio during the phonograph'ic reception thereby 44 is then inserted in reproduction. Plug jack 45 thus makingcontact respectively bemembers 42 tact members 43 and 48. Electric coil 36 is thus placedin electrical connection with the primary Winding o'f transformer l so that when stylus 26 is placed in engagement tween' contact with the grooves of a phonograph record thev electrical impulses Set up in said coil corresponding to the undulations of'such record are supplied to said transformer and such impulses are amplified inthe usual manner of therinionic tube amplification so as to produce, at the loud-Speaking or sound producing meansltl, sound of the desired intensity and possessing goody qualities of clarity and accuracy.

The insertion of plug 44 in jack 45 alsor causes connection to be closed a't 60 between Contact members 57 and 58 so that condenser 63 is connected in shunt across the terminals of e thel secondary winding of transformer 2'. rl`he function of such condenser is to by-pass therethrough the elecltric current impulses of relatively high frequency corresponding to the usual scratching noise produced in phonograpliic repro-. duction as above described and said condenser is therefore of such capacity as to by-pass substantially all impulses of such relatively high frequency While permitting substantially no by-passing therethrough of electric'current impulses of a frequency equal yto that of all Vsounds Within the range of ordinary phonograph reproduction. It has been found that for certain type's'of amplifying sets a condenser having acapacity` of from .O01 to .005 microfarads may advantageously be employed for this purpose. of such relatively high vfrequency current impulses through condenser 63 substantially prevents the flow of such high frequency iinpulses through the grid circuit of thermionic l tube 4 so that the amplifying impulses produced in the plate circuit of said tube and disconnectand 50 and con- "the same scheme also 'comprises as rlhe ley-passingsupplied to tially freeA quency impulses.

from the current supply circuit therefor,`

and to insert a compensating resistance iii series with the filaments of the remaining thus -preventing undue tubes of the circuit, deterioration of the filament of the detector `tube and also causing -the energization o`f the filaments of the remaining tubes to remain the same as though -the detector tube were connected in circuit. In illustrating this form of the invention has ybeen employed as in the other form, that is to say the portions of the normal circuit which are used only in connection with radio reception are shown in light dotted lines While the remaining portions of the normal system are shown in light solid lines, while thel parts of the circuit which are added for the purposes of my invention and which are used' in connectionwith electric phonograph reproduction are shown in heavy solid lines. In addition certain Wires which are added to the circuit for the purposes ofthis aspect of my invention and which vare employed only in connection with radio reception are shown in heavy dotted lines. The radio receiving 'set ,comprises essentially the same parts as shown in Fig. 1 and the switching device before contact members 48, 50, 57 and 58, which are connected in the same manner as ,before and also by-pass condenser 63 connected as before. In this case Ihowever the usual wire (indicated at in for connecting one of the filament Fig. 1) terminals of detector tube l2 tb the A battery is removed and wires 7 2 and 73 are substituted therefor. A suitable resistance 74 is connected ,in the filament circuits of the thermionic tubes 3 and 4, the'vvire 7 2 aforesaid being connected at one side of said resistance and another wire v7 4 being connected at the other side4 of said resistance. The jack indicated at 45 is providedin this case with additional contactsprings 7 (i, 77, and 78 which vare so arranged'that when plug 44 is inserted` in the jack the raising of contactspring 50 lifts an insulating pin 7 9 off ofy contact spring 7 6 Which then by its own resilience breaks connection with contacts 77 and 7 8. When, however, plug 44 is removed from the jack, pin 7 9 engages coritact sp ing 76 and moves the same into poiis sition to close connectionv with contact mem-- bers'77, and 78 andv 81 and 82 respectively;

example of the sa'mc construction as indicated in Fig. 1.

In the operation of thisform of the invenf tion the functions of the switching device in connecting the electrical phonograph reproducer to the input of transformer l and for connecting by-pass 'condenser 63 across the output terminals of transformer 2 when plug 44 is inserted in-jack 45 are performed in substantially the same, manner as above de`- scribed. It will be observed however that when the plug is so inserted connection is broken between contact member 76 and contact members 77 and 78 so that the filament of detectorltube 12 is disconnected from the A battery circuit. Furthermore resistance 74 is placed inseries with the filaments of amplifier tubes 3 and 4, said resistance being of sucli'value that when yso inserted the current flow in the filaments of said tubes is substantially the same as though saidv resistance were out'of the circuit andt-he filament of the detector tube were connected in the circuit. Therefore when plug 44 is inserted so as tov permit operation of the circuit for phonographic vreproduction purposesfthe filament of thedetector tube 12 is.

not energized and deterioration thereof is prevented, while the filaments of amplifier tubes 3 and 4 are energized or heated to the same intensity were in circuit.l f

When, however, plug44 is-removed from jack 45 connectionl is closed between contact member 76 and contact` members 77 and 78 and the filament circuit of detector tube 12 is thereby completed through wire 72, contact member 77, contact member 76, contact member 78, and wire 7 3. The detector tube is thereby energized so as to permit utilization of the circuit for radio reception purposes. At the same time however a shunt is placed across resistance 74, through wire 72, contact 77, contact 76, and wire 75. It is therefore seen that when the detector tube, as

`well as the amplifier tubes, are connected to the A battery terminals, resistance 74 is out of the circuit, while when the detector tube is disconnected from the A batterir terminals, said resistance is in the circuit, which results inluniform energization of the filaments of the amplifier tubes at all times whether 'thesame are being used in connection with radio as though thed'etector tube4 reproducing ydevice amplifier an electrical lamplifying reception or electrical phonograph reproduction. c i

I claim:

the amplifying system of .a radio receiving apparatus, an electrical phonograph reproducing device, electrical connections between said reproducing device and the input of said amplifying system, switching means included in said electrical connections for making and breaking connection between the reproducing 'device and the amplifying system, a condenser, means connecting said condenser in shunt across the secondary terminals of a transformer of saidy amplifying system, and means for automatically making and' breaking the connection between said condenser and said transformer upon operation of said switching means to respectively make and break the connection between the and the amplifying system. I

2. An apparatusassetforth in claim 1 and comprising in addition an electrical resistance means, and means for automatically disconnectinglthe filament of the detector tube of the radio receiving and for inserting said resistance in series in the filament circuit of the amplifying system, upon operation of said'switching means to make the connection between the reproducing device and the amplifying system.

An apparatus for electrical sound' reproduction comprising, in combination with system whose input is connected to radio signal detecting means, an electrical phonograph reproducing de 1. An apparatus lfor electrical sound reproduction, comprising 1n combi-nation with f vice, an electrical circuit connecting saldra'.

producing device to the input of said amplifymg system, a condenser, an electrical *circuit connecting said condenser in shunt, 

